Disinfection By-Product (DBP) Control Program

MWH was hired by the Antelope Valley – East Kern (AVEK) Water Agency in the Fall of 2003 to evaluate options for disinfection-by-product (DBP) control and design the improvements at their four surface water treatment plants (Quartz Hill – 90 mgd, Rosamond – 14 mgd, Eastside – 10 mgd, and Acton – 4 mgd). The source of raw water to all four plants is the East Branch of the California Aqueduct, one of the most challenging surface waters in the state. Following the design, the Agency hired MWH to manage construction of the projects under a Construction Management-at-Risk agreement.

In addition to process improvements, the Quartz Hill WTP will be expanded from 65 to 90 mgd. The Quartz Hill WTP has sufficient capacity in the existing filters for 90 mgd, but the clarifiers did not support this capacity. As part of the project, MWH designed modifications to the existing clarifiers to increase capacity by adding plate settlers, a new flocculation stage, new sludge collection system, new rapid mix, and expansion to chemical storage for aluminum sulfate and sodium hydroxide. Algae control (a major issue on East Branch water) is provided by fully enclosing the flocculation-sedimentation basins in a pre-engineered metal building.

Making modifications to AVEK’s existing water treatment plants is very complex and requires significant preconstruction planning and coordination to minimize the impact to ongoing plant operations. For example, MWH, AVEK and the trade contractor at the Quartz Hill WTP recently completed a successful 5-day shut down of the plant to make critical plant tie-ins and modifications. It was the first time since the plant was originally constructed in 1978 that the entire plant was shut down. During the 5-day period, more than 100 workers executed a day-by-day plan of activities that were carefully established in advance to ensure a successful shut down. Some of the activities included demolition and replacement of slide gates and valves, construction of new water channel walls, saw cutting of existing concrete walls to allow for future water passages and installation of new pipeline connections to structures. This successful plant shut down contributed to the projected early completion of the project.

Design

Engineering Services During Construction

Construction Management-at-Risk

Extensive modifications and enhancements to existing 30-year old water treatment facilities.

Complex sequencing and coordination of modifications at operating water treatment plant facilities.

Limited windows of opportunities for plant shut-downs to make critical tie-ins.